1. Field of the Invention
This invention relates to integrated circuit packaging capable of batch manufacture.
2. Brief Description of the Prior Art
Many integrated circuit packaging concepts are presently available for single and multiple semiconductor device applications. Commercial applications are typically potted while military applications use hermetic enclosures.
Devices are mounted on leadframes, interconnected using a wirebond process and subsequently potted with a dielectric material for single devices and commercial applications. A heat exchanger is bonded to the package when improved cooling is required.
When multiple devices are packaged as in integrated function, an internal interconnect is necessary. A package may include a Kovar housing with glass-to-metal feedthroughs for external interface. A multilayer interconnect substrate is adhered to the housing base. Devices are adhered to the substrate and interconnected using the wirebond process. A lid is attached to complete the enclosure. This typical packaging requires interconnect to be effected in a serial manner, one package at a time.
In accordance with the present invention, there is provided a low cost, batch manufactured package which achieves a size/weight reduction with improved high frequency operation as compared with prior art packages.
Briefly, there is provided a base, preferably cast, of good heat conducting material, preferably a metallized dielectric such as metallized alumina or metal, such as copper, nickel/iron or aluminum. The base is designed and fabricated to provide a plurality of packages thereon.
Each package in the base is defined by a first set of grooves extending entirely through the base material, one such groove on each side of the package. A second set of grooves is disposed at the corners of the package, each of the second set of grooves being connected to a pair of adjacent grooves but not extending entirely through the base material and forming a web. Thereby, each package is connected to each of the packages therearound by the retained portions of each of the second set of grooves. The combination of the two sets of grooves associated with each package provides a groove that completely encircles the package except for the web formed from the material disposed in each of the second set of grooves. The material in the second set of grooves is preferably of minimal dimension such that the material will break down when a minimum of force applied thereto, such as by a punch or the like.
Each package includes a recessed central region or cavity with active and/or passive elements, such as integrated circuits, inductors, capacitors, etc. being disposed within the cavity and secured there with an adhesive or the like. The elements within the cavity can optionally be potted therein with the remainder of the cavity being filled with a filled epoxy or other suitable potting material as is well known, it merely being necessary that bond pads be exposed for later connection when the cavity includes the potting material. An overlay, which is one or more layers of dielectric material, such as, for example, polyimide, includes patterned metallization of copper or aluminum thereon and is disposed on the top surfaces of the package, the metallization including conductors, inductors and the like and pads for connection to the pads on integrated circuits and/or passive devices within the cavity. Where the overlay includes plural layers of insulator and metallization, vias are provided through the insulator for interconnection between layers of metallization as well as to bond pads and the like in the components disposed within the cavity. Optional grooves can be provided on the side of the package opposed to the open end for the purposes of heat dissipation. These grooves can be initially molded into the cast base or can be machined into the base in standard manner.
In accordance with the present invention, the packages can all be fabricated together in their entirety or partially with completion of fabrication taking place after separation of the, packages from each other in the manner discussed hereinabove. The packages are separated by providing a punch or the like which removes the remaining base material in the grooves, this base material being the sole interconnection between packages. This remaining material can be removed from between all of the packages simultaneously by providing a punch with plural punch elements dimensioned to extend through all of the grooves. Alternately, a punch for one or more of the grooves can be provided to remove one or more of the packages from the base material. The result is that the packages will be separated from each other and include corner indentations.
As a further embodiment, the base can be a sheet of metal or the like of the same material as the housing described hereinabove with cavities or indentations therein to receive the active and/or passive elements, the manner of separation of the packages being as described hereinabove or by elimination of the apertures and simple between packages to provide the required separation.